The present invention refers to a safety braking device for a portable power saw, particularly a chain saw, of the type incorporating a rotatable brake drum coupled to the drive shaft of the power saw, a flexible brake element disposed about at least a part of said brake drum, and a control handle which cooperates with an actuating member, retained in operating position against the action of a spring and which is releasable by influence of the control handle for actuation of the brake.
Safety brake devices for power saws are arranged in such a manner that the accident risk at so called kickbacks of the power saw is reduced to a minimum. Safety brakes are earlier known and consist mainly of at least one brake drum coupled to the engine drive shaft, a moveably arranged control handle located in front of the gripping handle of the power saw, and being connected direct or via one or more actuation members to a brake element. The brake element is acted upon by one or more springs, whereby the control handle and the brake element are brought to take up their inactive position, at which the brake element is free from said drum. The control handle is arranged thus that the power saw when subjected e.g. to a so called kickback during operation the manual influence unintentionally caused by the saw operator on the control handle will result in a displacement thereof, whereby a biased spring force is released and urges the brake element to engagement against the brake drum rotating in the power saw. It is then generated a braking power, which is sufficient swiftly to retard the brake drum and the saw chain, whereby serious near-accidents are avoided. The drawbacks of the hitherto known safety brake devices are that they incorporate a plurality of components which have to be manufactured with more or less accuracy e.g. such as bearings, latchs etc, whereby the assembly and the manufacture will be expensive. In all cases it is used some type of a lever which can be swung about one or more pivots, and it is therefore necessary to dimension all the details forming part of the assembly comparatively coarse as they will be subjected to heavy stresses at braking. This will on one hand make the manufacture more expensive and it will on the other hand result in a more heavy power saw. A known fact is that the more details that are forming part of a mechanism the bigger is the risk for malfunctions and variations on the braking effect. As the safety brake device is an important safety arrangement on a power saw is it necessary that its function is very reliable. This is secured with a simple design with only a few components.